The fears: In the sixties, scientists linked aluminum—an ingredient in antiperspirants—to nerve cell damage in rabbits and theorized that the element might play a role in Alzheimer's. There has also been speculation that antiperspirants could cause cancer by blocking sweat glands from expelling toxins. In 2004 a study in the Journal of Applied Toxicology reported finding parabens, widely used preservatives, in breast cancer tumors, and suggested that underarm cosmetics, like antiperspirants and deodorants, may be to blame.
The facts: "There is no evidence that aluminum is linked to the cause or progression of Alzheimer's disease," says William Pendlebury, MD, professor of pathology at the University of Vermont College of Medicine in Burlington. The toxin-trapping theory is also unfounded: "The idea that antiperspirants block the excretion of toxic substances is just plain wrong," says Michael Thun, MD, head of epidemiological research at the American Cancer Society. "We sweat principally as a way to control body temperature. Our bodies get rid of toxic and carcinogenic substances by excretion in stool or urine and through metabolism by the liver." The paraben issue is a bit trickier, because these preservatives can mimic estrogen in our bodies, and breast cells—including cancerous ones—tend to multiply in the presence of estrogen. However, "parabens are exceedingly weak estrogens, and when used in the minuscule amounts found in cosmetics, they have absolutely no effect," says Bergfeld. (Which means the parabens found in your moisturizers, cleansers, and haircare products are also safe.) And a recent study in the Journal of the National Cancer Institute concluded that antiperspirant use does not increase one's risk for breast cancer. In fact, most antiperspirants and deodorants don't even contain parabens (you might find them in water-based roll-ons, says Hammer, but not in sticks or sprays).
The fears: Phthalates, a group of chemicals with many uses, are sometimes added to perfumes to prolong their life. Several studies have shown that certain phthalates can cause developmental abnormalities in male rats and humans. Researchers evaluating 379 men from an infertility clinic have also linked phthalate exposure to sperm damage. Another potential perfume risk: synthetic musks, the earthy base notes found in many fragrances. There are several kinds, and traces of certain ones have turned up in human fat tissue and breast milk, indicating that they can penetrate the skin. Some musks have been shown to be weak endocrine disrupters and cause neurological problems in animals, and can bring on contact dermatitis (red, itchy skin) and photosensitivity in humans.
The facts: "The diethyl phthalate [DEP] used in perfume poses no reproductive or developmental problems," says Foster, of the National Toxicology Program. (It was dibutyl phthalate, or DBP, that harmed the rats, and primarily DBP metabolites that were implicated in human studies.) After scrupulous testing, the CIR and the European Union's Scientific Committee on Consumer Products (the EU's equivalent of CIR) deemed DEP safe. The same is true for the synthetic musks used in cosmetics, says Jean-Pierre Houri of the Research Institute for Fragrance Materials (RIFM), the agency that assesses fragrance ingredients. "Mainly four musks are used today, and all have been proved safe," says Houri, adding that, in some cases, RIFM limits the amount of musk a scent can contain to further ensure safety.